This invention relates to grinding mills. Grinding mills are used for pulverizing materials or mixing them to prepare them for analysis. Typically, grinding mills grind cement mix, rocks, slags, soils, ceramics, and ores. They have also been used for hundreds of other materials including sulfur pellets, dried marsh-grass, pharmaceuticals, and other materials which are reasonably brittle or are rendered brittle by some suitable means, such as cryogenic cooling.
More particularly, the present invention relates to swing mills. Swing mills generate motion in an orbital fashion and cause an element to move within a container, thereby grinding the contents of the container. Conventional swing mills, such as those sold by the assignee under the trade name SHATTERBOX.RTM., swing a dish-shaped grinding container in a tight, high-speed circle. Inside the dish are the sample to be ground, a puck, and (in larger containers) a ring. Grinding in the swing mill is performed by imparting different motions to the dish and puck or ring (hereinafter, any references to puck should be understood to include, under suitable circumstances, a ring or rings or other hard objects, such as various sized balls, which can move freely within a container). The dish is caused to orbit about some point other than its center point and the puck is allowed to move freely within the dish. As these grinding elements swing free inside the dish, the sample is rapidly crushed between the walls of the dish and the grinding elements, and further attrited by the millstone-like action of the puck against the container floor (thus the name "swing mill").
The main issue in swing mill design is causing the dish to orbit around some point other than its own center point without rotating the dish around its own center point. Causing rotation of an object around its own center point is not difficult because a conventional motor can provide rotational force. However, causing an object to orbit without rotating presents a more complex design problem. This type of action is required to create the grinding motion of the puck within the dish. The present invention addresses this design problem.
Generally, conventional swing mills that create the above-mentioned motion are large, immobile pieces of laboratory machinery. A small swing mill that can be used on a bench-top is especially advantageous because it affords easy access to the swing mill, provides transportability of the swing mill for fieldwork, saves space in the laboratory and allows the user to move the swing-mill around within the laboratory.
Therefore, it would be desirable to provide a grinding mill that utilizes a simple and cost-effective mechanism to grind a sample.
It would also be desirable to provide a mill that is relatively light and occupies a small area of space so that the mill can be easily transported.
It would also be desirable to provide a mill that is relatively short so that the mill can be easily loaded and unloaded in a bench-top environment.